It is already prior art to decorate glass objects by a firing process, usually for decorating in gold, which is a particularly expensive and difficult process. The substantial cost is in the use of real gold for gilding, which represents a cost even when the weight of gold is very small, owing to the limitation of the area gilded and its extreme thinness. Even the firing process itself is costly, and there is absolutely no way of recovering any rejects, which therefore represent a further clear cost. The objects have to be handled many times because, after production of the glass objects, there must be application of the decoration, then handling to reintroduce the decorated objects into a kiln, avoiding contact and possible consequent irregularities in the decoration, then a second firing to stabilize the decoration, and finally removal of the objects from the kiln and inspection thereof and discarding of any rejects. The rejects may be numerous and are, as stated, irrecoverable.
Other processes offer different difficulties and problems, including problems with wear resistance.